Selective conversion of normal paraffins



Dec. 27, 1966 R. M. BUTLER ETAL 3,294,858

' SELECTIVE CONVERSION OF NORMAL PARAFFINS Original Filed June 13, 19585 Sheets-Sheet l GASES PRODUCT OIL FEED OXYGEN FIG.

Jackson Eng Roger M. Butler lnven'fors fl/ Po eni' Agent Dec. 27, 1966R. M. BUTLER ETAL 3,294,858

SELECTIVE CONVERSION OF NORMAL PARAFFINS Original Filed June 13, 1958Sheets-Sheet 2 EFFECT OF CONTACTING TEMPERATURE UPON POUR POINTREDUCTION 600F7 o l /IO|OF. o IO l A l A 850F. U 5 I E D E 3 4O 5 0/ 8"5O a E FEED: 560658" F. GAS on. o 60 u/ FEED POUR POINTZ-I-F. A FEEDRATE: 0.5 w/w/ HOUR CONTACTING PRESSURE 750mm. H a I o I00 I50 200CUMULATIVE PRODUCT, GMS./IOO GMS. SIEVE ADJUSTED TO 575 F. INITIALBOILING POINT FIGFZ Jackson Eng Roger M. Butler Invenfors Pqiem AgentDec. 27, 1966 Original Filed June 13, 1958 CAPACITY, GRAMS/IOO GRAMSSIEVE R. M. BUTLER ETAL 3,294,58

SELECTIVE CONVERSION OF NORMAL PARAFFINS EFFECT 5 Sheets-Sheet 3 OFCONTACTING TEMPERATURE UPON SIEVE CAPACITY 0 F POUR POINT PRODUCTADJUSTED TO 575F. INITIAL BOILING POINT Feedi 560-658 F. Gas Oil FeedPour Pointl I 40F. Feed RoteI 0.5 W/W/Hour 25 ConIocIing Pressurel 750mm.Hg.

600 700 800 900 I000 l IOO CONTACTING TEMPERATURE, F.

F I G? 3 Jackson Eng Invenrors Roger M. BurIer PuIenI Ageni' UnitedStates Patent @tlice 3,294,858 Patented Dec. 27. 1966 Claims. Cl.260683) This application is a divisional application of Serial No.741,906, filed June 13, 1958.

The present invention relates to the upgrading of hydrocarbon oils andmore particularly relates to an improved process for eliminating normalparatlin hydrocarbons from oils in which they are present in admixturewith other hydrocarbons which comprises contacting such oils with ametallic alumino-silicate having uniform pore spaces of about 5 Angstromunits under conditions such that normal paraffins are continuouslyadsorbed into the alumino-silicate and continuously converted to olefinswhich are recovered with the non-adsorbed constituents of the oil.

The invention in a preferred embodiment is a process for lowering thepour point of a middle distillate, boiling between 300 and 650 F., bytreating it in the vapor phase with a 5 A. alumino-silicate at atemperature between 800 and 900 F. and at a space velocity of 0.3 to 1.2lb./ 1b., removing any by-product boiling below 300 F. and recondensingthe vaporized product.

Because of their low octane value in gasolines and their adverse effectupon the pour point and cloud point of hydrocarbonoils generally, normalparaffins are undesirable in high octane gasolines, aviation turbo-jetfuels, kerosines, heating oils, lubricating oils and other premiumquality petroleum products. Recognition of this fact has spurred effortsto develop processes which will permit the removal of normal parafiinsfrom oils intended for use in the manufacture of such products. One ofthe most promising methods proposed for separating normal paraffins frombranched chain and cyclic compounds developed to date involves the useof adsorbents which are selective for the normal parafiin molecules.These adsorbents, generally referred to as molecular sieves, arecrystalline metallic alumino-silicates containing a large number ofsubmicroscopic cavities interconnected by many smaller pores or channelswhich are extremely uniform in size. Molecules having afiinity for thealumino-silicate and small enough to enter the pores or channels arereadily adsorbed, while those of greater size or lacking such affinityare rejected. By employing alumino-silicates having uniform pore spacesof about 5 Angstrom units in diameter, excellent separations betweennormal paraffins and other hydrocarbons present in hydrocarbon oils canbe made.

The scientific and patent literature contains numerous references to thecomposition and adsorbing action of metallic alumino-silicates. Ingeneral these are crystalline zeolites containing an alkali or alkalineearth metal, aluminum, silicon and oxygen. They may be either natural orsynthetic in origin and may have uniform pore spaces of from about 3 toabout 15 Angstrom units, depending upon their composition and theconditions under which they were formed. As mentioned above, thosehaving pores of about 5 Angstroms are useful for separating normalparalfins from branched chain and cyclic compounds. Among the naturalzeolites having molecular sieve properties may be mentioned analcite,

and chabasite, CaAl Si O 6H O. Synthetic zeolites having similarproperties are described in US. Patent No. 2,306,610, where a materialof the formula (021N512) A12Si4012 is set forth, and in US. Patent No.2,522,426, which discloses a composition having the formula 4CaO A1 04SiO Other molecular sieves are described in articles by Brack andothers which were published in the Journal of the American ChemicalSociety, volume 78, page 593 et seq. in December 1956.

Despite the excellent selective adsorption properties of molecularsieves, certain difficulties have been encountered in attempting toapply them to the large scale removal of normal paraflin hydrocarbonsfrom branched chain and cyclic hydrocarbons. In using such adsorbents,it is necessary to employ a two-step cyclic process, The normalparaflins must first 'be selectively adsorbed upon the molecular sieve.Usually this is accomplished by contacting the oil with the adsorbent attemperatures in the range of from about to about 600 F. and at pressuresof from about atmospheric to about 100 p.s.i.g. Following thisadsorption step, the molecular sieve must next be reactivated by adesorption step before it can be used for adsorption again. Thedesorption step is usually carried out by steaming the used adsorbent,evacuating it, or displacing the adsorbed compounds by means of a gaswhich .is not itself adsorbed by the sieve. The capacity of molecularsieve adsorbents when used in this manner is very low and therefore suchcyclic processes are relatively expensive because of the frequency withwhich the sieve must be desorbed. The desorption methods available areonly partially effective and the selectivity and capacity of the sieverapidly decline as it is used. A further difliculty is that carbonaceousdeposits rapidly build up on the surface of the sieve. Regeneration ofthe sieve at frequent intervals by heating it to very high temperaturesor by employing other regenerative techniques alleviates this latterdifficulty to some extent but very frequent regeneration shortens theactive life of the sieve. Because of these difiiculties, the cost ofeffecting separations between hydrocarbons by means of molecular sievesis inordinately high.

The present invention provides a new and improved method for eliminatingnormal paraffins from hydrocarbon oils by means of molecular sieveswhich is free from many of the disadvantages associated with molecularsieve processes employed in the past. The process differs from priorprocesses in that molecular sieves are employed to effect chemicalconversion of the normal parafiins upon a selective basis, rather thanmerely a mechanical separation. It has been found that normal paratfinspresent in a hydrocarbon oil can be selectively converted to olefins bycontacting the oil with a molecular sieve having pore diameters of aboutA. under critical conditions. It is believed that the explanation forthis selective conversion phenomenon lies in the fact that gas phaseconfigurations are not possible in the pores of molecular sieves. It isimpossible for a normal paraffin molecule to rotate in the 5 Angstrompores of a molecular sieve except on its longitudinal axis and thereforethe rotations corresponding to the three main moments of inertia of themolecule become vibrations as the molecule is occluded in the sieve.This results in a high loss in energy of the molecule over an extremelyshort period of time. By providing the molecule with a sufficiently highinitial energy, it is possible to use this energy loss to effect ruptureof bonds in the molecule and convert the normal parafiins into lowermolecular weight olefins before complete occlusion takes place. Theolefins are not retained by the sieve but instead are recovered with thenon-adsorbed isoparaffins and cyclic compounds in the oil.

Regardless of the theoretical explanation for the phenomenon which takesplace, the process of the invention has numerous advantages overprocesses which have been proposed for the removal of normal parafiinsfrom hydrocarbon oils by means of molecular sieves in the past. Sincethe normal parafiins which would otherwise be occluded by the sieve arecontinuously converted to olefins which are not retained on the sieve,the pores of the sieve remain relatively free of hydrocarbons. Nodesorption step is necessary and the difficulties encountered indesorbing the sieve in prior processes are thus avoided. Olefins formedin the process can readily be separated from saturated constituents inthe oil and form a valuable by-product. The simplified procedure andequipment employed make the process considerably more attractive from aneconomic standpoint than processes utilized heretofore.

Molecular sieve adsorbents suitable for use in the process of theinvention are available commercially and may be produced in a number ofways. One suitable process for preparing such adsorbents involves themixing of sodium silicate, preferably sodium metasilicate, with sodiumaluminate under carefully controlled conditions. The sodium silicateemployed should be one having a ratio of soda to silica between about0.8 to 1 and about 2 to 1. Water glass and other sodium silicatesolutions having lower soda to silica ratios do not produce theselective adsorbent crystals unless they are subjected to extended heatsoaking or crystallization periods. Sodium aluminate solutions having aratio of soda to alumina in the range of from about 1 to 1 to about 3 to1 may be employed. High soda to ilumina ratios are preferred and sodiumaluminate solutions having soda to alumina ratios of about 1.5 to 1 havebeen found to be eminently satisfactory. The amounts of the sodiumsilicate and sodium aluminate solutions employed should be such that theratio of silica to alumina in the final mixture ranges from about 0.8 to1 to about 3 to 1 and preferabl from about 1 to 1 to about 2 to 1.

These reactants are mixed in a manner to produce a precipitate having auniform composition. A preferred method for combining them is to add thealuminate to the silicate at ambient temperatures using rapid and efficient agitation to produce a homogeneous mixture. The mixture is thenheated to a temperature of from about 180 to about 215 F. and held atthat temperature for a period of from about 0.5 to about 3 hours orlonger. The crystals may be formed at lower temperatures but in thatcase longer reaction periods are required. At temperatures above about250 F. a crystalline composition having the requisite uniform size poreopenings is not obtained. During the crystallization step, the pH of thesolution should be maintained on the alkaline side, at about 12 orhigher. At lower pH levels, crystals having the desired properties arenot as readily formed.

The crystals prepeared as described above have pore diameters of about 4Angstrom units. To convert these to crystals having 5 Angstrom pores, itis necessary to employ a base exchange reaction for the replacement ofsome of the sodium by calcium, magnesium, cobalt, nickel, iron or asimilar metal. Magnesium, cobalt, nickel and iron have greater crackingactivity than does calcium and therefore it will often be preferred toemploy solutions of these metals for replacement purposes.

The base exchange reaction may be carried out by water washing thesodium alumino-silicate crystals and adding them to a solutioncontaining the desired replacement ions. An aqueous solution ofmagnesium chloride of about 20% concentration, for example, may be usedfor preparation of the magnesium form of the 5 Angstrom sieve. After acontact time which may range from about 5 minutes to about an hour, the5 Angstrom product is filtered from solution and washed free of theexchange liquid. About 50 to 75% of the sodium in the crystals isnormally replaced during the base exchange reaction.

The crystals thus prepared are in a finely divided state and are usuallypelleted with a suitable binder material before they are calcined inorder to activate them. Any of a number of binder agents used in themanufacture of catalysts may be employed for this purpose. A binderconsisting of bentonite, sodium silicate and water, for example, hasbeen found satisfactory. In using this binder, the constituents shouldbe mixed so that the product contains from about 5 to 10% bentonite, 5to 15% sodium silicate and about 75 to of the crystals on a dry basisand that the total mixture contains about 25 to 35% water. This mixturemay then be extruded into pellets or otherwise shaped and subsequentlydried and calcined. Calcination temperatures of from about 700 to about900 F. or higher are satisfactory.

In carrying out the process of the invention, the feed stream iscontacted with the molecular sieve adsorbent in vapor phase at atemperature of from about 800 to about 1000 F. At temperatures belowabout 800 F. little conversion takes place and therefore removal ofnormal parafiins from the oil is low. At temperatures above about 1000 Fconsiderable thermal cracking of isoparaffinic and cyclic constituentsof the oil takes place and hence much of the selectivity of the processdisappears. Contacting temperatures of from about 800 to 900 F. are mosteffective and a temperature of about 850 F. is particularly preferred.

The pressures employed in contacting the oil with the adsorbent mayrange from about 50 mm. of mercury to about psi. Generally it ispreferable to carry out the contacting step at about atmosphericpressure. The feed rate employed may range from about 0.1 to about 3pounds of oil per pound of molecular sieve per hour. Preferred ratesrange between 0.1 and 1.0 pounds per pound per hour. Under theseconditions, normal parafiins present in the oil will be selectivelyconverted to lower boiling olefins which are not retained upon the sieveand instead are discharged with the product oil. These olefins may bereadily separated from the oil and constitute a valuable by-product ofthe process.

Although the olefins formed by the selective conversion of normalparafiins in the process are not retained upon the sieve, depositsgradually build up on the sieve surface, probably due to polymerizationof the olefins. Sulfur compounds, water and other contaminatingmaterials present in the feed may also contribute to the gradualaccumulation of such deposits. In order to remove these deposits andmaintain the activity of the adsorbent at a high level, the sieve isregenerated at suitable intervals. Although steam and other regenerationprocedures heretofore disclosed may be employed in this step of theprocess, it is normally preferred to regenerate the sieve by passing astream of oxygen-containing gas through the sieve bed at hightemperatures. In the presence of the oxygen, the deposits are burnedfrom the surface of the sieve and the sieve activity is restored. Thequantity of oxygen required for this burning step is small, since thetotal amount of foreign matter on the sieve is small, and therefore gasstreams containing as little as 5% oxygen may be used. It is preferred,however, to employ air for this purpose. The air or other gas streamused in the regenerative step may be preheated to a temperature of fromabout 500 to about 800 F. before contacting it with the sieve. The hightemperature zone formed by combustion of the deposits upon the sievesurface proceeds through the adsorbent mass rapidly and exists at anyone spot for only a brief inst-ant. It has been found that the sievecrystals are not appreciably impaired by this regenerative treatment.

In order to further minimize deposit formation and reduce the frequencyof regeneration, it is often advantageous to contact the feed streamwith a guard bed of alumina, silica gel or a similar adsorbent prior tointroducing it into the treating zone. Polar contaminants in the feedare removed by the guard bed and hence the formation of deposits withinthe treating zone is reduced. The guard bed may be regenerated byburning or other conventional techniques.

In order to further reduce deposit formation within the treating zone,it is preferred to carry out the process in the presence of addedhydrogen, nitrogen, carbon dioxide or a similar gas having a moleculardiameter smaller than the pore diameter of the sieve. The presence ofsuch a gas serves to purge hydrocarbon fragments from the pores of themolecular sieve and prevent the reaction of such fragments to formcarbon and polymeric deposits. Hydrogen is particularly preferred forthis purpose because it may also result in saturation of some of theolefins produced and thus further reduce deposit formation. The use ofhydrogen is particularly effective in the presence of metallicalumino-silicate adsorbents which have some hydrogenation properties.The nickel form of 5 A. molecular sieve, for example, tends to causehydrogenation of the olefin to a greater degree than does the calciumform and therefore deposit formation is reduced. The gas employed may beintroduced with the feed at a rate such'that its concentration in thereactor ranges from about 5 to about 95 mole percent.

The oils adapted for treatment in accordance with the process of theinvention may in general be defined as hydrocarbon oils boiling in therange between about 100 to about 750 F. and especially between 320 and650 F.

Such oils include naphthas. kerosine (boiling between 320 and 555 F.)and middle distillates and are widely used for the production ofgasolines, jet fuels, diesel fuels, heating oils and similar productswherein the content of normal parafiins must be limited to controlundesirable effects such as solidification in storage at low temerature. The process of the invention is particularly effective forremoving wax and similar normal paraffinic constituents from middledistillate petroleum fuels in order to reduce their pour point, cloudpoint and haze point, and it is in this area that the process of theinvention Will find widest application.

The exact nature and objects of the invention may be more readilyunderstood by referring to the following detailed description of apreferred embodiment of the process, to the examples set forthhereafter, and to the attached drawings in which:

FIGURE 1 depicts a flow diagram of a preferred embodiment of the processof the invention;

FIGURE 2 is a graphical representation of data showing the effect ofcontacting temperature upon the reduction in pour point of a gas oiltreated in accordance with the invention; and

FIGURE 3 is a graphical representation of data illustrating the effectof contacting temperature upon sieve capacity in the treatment of a gasoil in accordance with the invention.

Referringnow to FIGURE 1 a hydrocarbon oil containing normal panafilnsas well as iso-paraffinic and cyclic compounds, a gas oil boiling in therange of from about 450 to about 700 F., for example, is introducedthrough line 1 into furnace 2 where it is preheated to a temperature ofabout 850 F. The preheated feed, now in vapor phase, is passed throughline 3 and valve 4 into contacting zone 5. Hydrogen or a similar gashaving a molecular diameter less than 5 Angstrom units may be introducedwith the vaporized feed into zone 5.- The contacting zone has disposedtherein a bed of molecular sieve having uniform pore diameters of 5Angstrom units. ing zone may be fitted with suitable jacketing, heatcoils or similar means for controlling temperature within the bed. Thefeed stream passes upwardly through the adsorbent bed and in so doing,normal parafiins present therein are selectively converted to lowermolecular weight olefins. Some light gases are [also formed. The vaporstream after contact with the adsorbent is removed overhead fromcontacting zone 5 through line 6 containing valve 7 and is passed tocondenser 8. In the condenser, hydrocarbons boiling above about F. arecondensed and taken off as a bottoms product through line 9. Uncondensedgases are removed overhead through line 10. The product oil recoveredthrough line 9 may be further fractionated to remove constituentsboiling below the feed boiling point if desired. The overhead gas streammay be passed to a light ends plant for separation and recovery of theindividual gaseous constituents.

The contacting procedure described above is continued until theconcentration of normal panafiins in the product stream withdrawnthrough line 9 reaches an unacceptable level. This concentration mayreadily be determined by ultra violet analysis, infra red analysis,refractive index determination or the like. At this point sufiicientdeposits have formed upon the sieve surface to require regeneration ofthe sieve. Introduction of the feed stream is therefore halted andfollowing nitrogen or other inert gas, air or other oxygen containinggas is introduced into the bottom of contacting zone 5 through line 11containing valve 12. The gas stream should .be preheated to atemperature of from about 500 to 800 F. This may be accomplished in asuitable furnace, not shown. Under the temperature conditions prevailingwithin the sieve bed, oxygen inthe gas stream combines with the depositson the sieve surface and the deposits are burned off. The combustiontakes place within a narrow zone which moves from the bottom of the bedto the top of the bed. At any instant the temperature within thecombustion zone may range from 1000 to 1500 F. but because of the shorttime during which these temperatures prevail at any level in the bed,crystallinity of the sieve is not materially affected. Gases are removedoverhead from the contacting zone through line 13 containing valve 14.Upon completion of the regenerating step of the process, valves 12 and14 may be closed and valves 4 and 7 opened to permit resumption of thecontacting step. Although only one contacting vessel is shown in FIGURE1, it will be understood that in most cases it will be advantageous toemploy two or more vessels suitably connected in parallel to permitregeneration of the spent sieve without interruption of the process. Thearrangement of such vessels will be obvious to those skilled in the art.

The process of the invention is further illustrated by the followingexamples.

EXAMPLE 1 A petroleum middle distillate boiling between about 326 F. andabout 680 F. was contacted with a calcium The contactform molecularsieve having uniform pore diameters of Angstrom units by passing thefeed stream downflow through a fixed bed containing 500 grams of thesieve. The contacting temperature was 850 F. and the pressure was about760 mm. of mercury. The feed rate averaged 1 pound of oil per pound ofsieve per hour. This contacting was continued until about 750 grams ofthe oil had been passed through the sieve bed. At this point theoperation was discontinued and the product collected was analyzed. Asimilar run was then made in which the feed stream was contacted withthe sieve at a temperature of 390 F. and at a pressure of 0.2 mm. ofmercury. Again the product recovered from the contacting zone wascollected and analyzed. Inspections of the feed stream and EXAMPLE 2 Amixed blend gas oil boiling between 575 and 658 F. was passed through abed containing 850 grams of a 5 A. calcium molecular sieve attemperatures of from 600 to about 1000 F. Data collected in these runsare shown in Table II below.

Contacting Temp. F Pressure, mm. Hg- Rate, W./W./Hr

Feed Treated, g/lUO g. sieves" Total Product, g./100 g. sieves Wt.Percent on feed Material retained on sieve, g./100 g.

sieves Product Distribution, wt. Percent on feed:

Gas (0 and lighter) Naphtha (C -325 F.V.T.) Product (325575 F.V.T.) (575F. 1. Material retained on sieves Material Balance 1 Sieves wereconsidered saturated when products boiling above 575 F. showed noimprovement in pour point compared to fresh feed.

2 Poor material balance believed to be caused by loss of gas.

the products from these two operations are shown in Table I below.

Table l INSPECTIONS OP FEED AND PRODUCTS ASTM D-158 Distillation Feed850 F. 390 F.

Product Product I.B.P 326 108 328 5%.- 369 180 362 107 385 320 378 2 415352 406 440 418 430 472 456 456 50%- 504 502 488 60%. 533 534 520 70%-562 560 552 80%- 592 579 58a 90%. 623 592 520 95%- 642 598 654 F.B. 680652 676 Four Point, F--- +5 *-55 40 Cloud Point, F +16 *-55 32 R1. at 20(L- l. 4630 *1. 4737 1. 4662 Bromine No--. 0. 4 17. 1 0.5

850 F. product adjusted to 325 F. initial boiling point.

From the distillation data set forth in the above table it can be seenthat an appreciable quantity of low boiling material was formed in therun carried out at 850 F., while essentially none was formed during thelow temperature run. The initial 10% of the product collected in the 850F. run had an extremely high bromine number,

In order to differentiate between the benefits due to selectiveconversion of normal parafiins and benefits which might be due tocracking, only material boiling above 575 F. was considered indetermining the saturation or exhaustion point. The data show that theamount of feed which can be treated before saturation occurs isconsiderably greater at temperatures of 850 F. and higher. A temperatureof 850 F. showed the most favorable results. At that temperature thetotal product yield was about 86%, based on the feed. With increasingtemperatures, this value decreased appreciably with a correspondingincrease in the production of gases. This indicates that a non-selectivecracking occurs when too high a temperature is used. Material retainedon the sieve at a temperature of 1010 F. was greater than that retainedat any of the lower temperatures. This again appeared due largely tonon-selective cracking but may also be attributable to increasedpolymerization of olefins at the higher temperature.

EXAMPLE 3 The products obtained in the runs described in the previousexample were analyzed and their inspections are set Table III PRODUCTINSPECTIONS Mixed Blend Gas Oil Treated with A. Molecular SievesContacting Temp., F Liquid Product:

Samples of the product obtained at intervals during the runs describedin Example 2 were tested to determine their pour points. These sampleshad been flashed to an initial boiling point of 575 F., approximatelythe initial boiling point of the feed, in order to avoid distortion ofthe results that would otherwise have been caused by the prsence of thelow boiling cracked materials, which naturally have low pour points.These pour point data are shown in FIGURE 2 of the drawing. From thefigure it can be seen that greater quantities of considerably lower pourpoint product can be obtained by contacting the feed at temperatures of850 to 900 F. than can be obtained by treating the feed at higher orlower temperatures. At the lower temperatures the sieve rapidly becomessaturated and little further improvement in pour point results. At hightemperatures above about 1000 F. non-selective cracking takes place andthe pour point is not improved as much.

EXAMPLE 5 Based on data obtained in the runs set forth in Example 2,sieve capacity at various temperatures for a 0 F. pour point product wasdetermined. The results of these determinations are shown in FIGURE 3.The data thus presented illustrate the critical effect of the contactingtemperature upon sieve capacity. At a temperature of about 850 F.capacities in excess of 100 grams per 100 grams of sieve are obtained.At temperatures higher than 950 F., or lower than 800 F., capacityrapidly falls off.

EXAMPLE 6 In order to determine the effect of contacting pressure uponthe selective conversion of normal paratfins, a gas oil was contactedwith a 5 A. molecular sieve at a temperature of 980 F. and 750 mm. ofmercury. A sample of the same gas oil was then tested under similarconditions except that the pressure was reduced to 200 mm. of mercury.It was found that the reduction in pressure improved the selectiveconversion of normal paratfins somewhat. This improvement, however, didnot increase the yield of accumulative product in excess of thatobtained at 850 F. and 750 mm. of mercury. Operation under the latterconditions is therefore to be preferred.

EXAMPLE 7 A number of runs were also conducted at a feed rate of 1.5w./w./ hr. and the results obtained were compared with those obtained inearlier runs carried out at 0.5 w./ w./hr. It was found that increasingthe feed rate from 0.5 to 1.5 w./w./hr. without changing the temperaturegave a lower yield of good product. By increasing the temperature to 950F., however, it was possible to operate at the higher feed rate withoutany significant reduction in sieve capacity over that obtained at 850 F.with the lower feed rate.

' EXAMPLE 8 Table IV TREATMENT OF 08 NAPHTHA 1100 F., p.s.i.g.

Liquid Product Components, Vol. Percent Feed Product n-Hexan 52. 3 36. 1O6 Isoparatfins 30. 4 30. 3 Co Naphthenes 11.3 9.0 Other typeHydrocarbon 6.0 24. 6 Ratio n-Hexane to Isop.+Naphthen 1. 25 0.92

From the above :table it can be seen that the ratio of normal hexane toisoparafiins and naphthenes decreased from 1.25 to 0.92, indicating thatnormal paraflins were converted in the presence of the molecular sieve,in preference to isoparafiins and naphthenes. Under the conditions whichhave been found necessary for carrying out the process of the invention,thermal cracking does not occur to a significant extent and thereforethe improvement in the ratio of straight chain compounds to isoparafiinsand naphthenes would be considerably higher.

EXAMPLE 9 Samples of a mixed blend heavy atmospheric gas oil having anASTM boiling range between 560 and 658 F. and a pour point of +40 F.were contacted with a 5 A. molecular sieve in the presence and in theabsence of added hydrogen in order to demonstrate the eiteot of a gashaving a molecular diameter less than that of the sieve upon the processof the invention. The contacting temperature employed was 850 F.Pressure within the contacting zone was held at 750 mm. of mercury. Thefeed rate in both cases was 0.1 pound of feed per pound of sieve perhour. In the first run no hydrogen was used and in the second hydrogenwas introduced with the feed at a rate such that the hydrogenconcentration in the reactor was 90 mole percent. The results obtainedin these two parallel runs are shown in Table V below.

Table V EFFECT OF ADDED HYDROGEN UPON CONVERSION OF NORMAL PARAFFINS*Product adjusted to 325 F. initial vapor temperature.

Referring to Table V, it can be seen that the presence of the addedhydrogen in Run B resulted in an increase in sieve capacity of about 40to 45% and an increase in yield, based upon feed, of about over thevalues obtained in Run A. This improvement is shown with respect to boththe 0 and the 30 F. product. The bromine numbers of the two productsindicate that the improvement was primarily due to the purging of thegas, rather than hydrogenation of olefins, although some hydrogenationdid occur. From this it can be seen that the improvement obtained is notlimited to the use of hydrogen and that other gases, nitrogen forexample, may be used as purging agents during the contacting step of theprocess. The improvement due to the use of such a purging agent is asignificant one and for this reason it is preferred to employ such anagent.

What is claimed is:

1. An improved process for selectively removing normal paraffinhydrocarbons from a hydrocarbon oil boiling between about 100 and about750 F. which comprises about 800 to about 1000 F. in a contacting zone,said gas selected from the group consisting'of hydrogen, nitrogen,carbon dioxide and inert gas, withdrawing oil vapor containing olefinsformed by the selective conversion of normal paraffins from said zone,continuing said contacting until the vapor withdrawn has an undesirablyhigh normal parafiins content, and thereafter regenerating said metallicalumino-silicate by contact with an oxygen-containing gas at elevatedtemperature.

2. A process as defined by claim 1 wherein said oil is contacted withsaid metallic alumino-silicate at a temperature between 850 and about1000 F.

3. A process as defined by claim 1 wherein said oil is contacted withsaid metallic alumino-silicate with concomitant purging with nitrogengas.

4. A process as defined by claim 1 wherein said oil is contacted withsaid metallic aluminosilicate with concomitant purging with from about 5to about mole percent of said gas having a molecular diameter less thanabout 5 Angstrom units.

5. An improved process for selectively converting normal paraifins in ahydrocarbon oil to olefins which oomprises contacting said oil in vaporphase at a temperature of from about 800 to 1000" F. with a crystallinemetallic 'alumino-silicate having uniform pore spaces of about 5Angstrom units in a contacting zone and concomitantly purginghydrocarbon fragments from the said pores of the crystalline metallicalumino-silicate with a gas having a molecular diameter less than about5 Angstrom units, said gas being selected from the group consisting ofhydrogen, nitrogen, carbon dioxide and inert gas, and Withdrawing fr-omsaid zone an oil having a reduced normal paraflins content and anincreased olefins content.

References Cited bythe Examiner UNITED STATES PATENTS 2,93 5,459 5/ 1960Hess et a1. 260676 2,952,630 9/1960 Eggersten et al 260676 3,033,7785/1962 Frilette 208 3,039,953 6/1962 Eng 208120 DELBERT E. GANTZ,Primary Examiner.

C. E. SPRESSER, Assistant Examiner.

1. AN IMPROVED PROCESS FOR SELECTIVELY REMOVING NORMAL PARAFFINHYDROCARBONS FROM A HYDROCARBON OIL BOILING BETWEEN ABOUT 100* AND ABOUT750*F. WHICH COMPRISES CONTACTING SAID OIL IN VAPOR PHASE WITH ACRYSTALLINE METALLIC ALUMINO-SILICATE HAVING UNIFORM PORT SPACES OFABOUT 5 ANGSTROM UNITS AND CONCOMITANTLY PURGING HYDROCARBON FRAGMENTSFROM THE SAID PORES OF THE CRYSTALLINE METALLIC ALUMINO-SILICATE WITH AGAS HAVING A MOLECULAR DIAMETER LESS THAN ABOUT 5 ANGSTROM UNITS AT ATEMPERATURE OF FROM ABOUT 800 TO ABOUT 1000*F. IN A CONTACTING ZONE,SAID GAS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, NITROGEN,CARBON DIOXIDE AND INERT GAS, WITHDRAWING OIL VAPOR CONTAINING OLEFINSFORMED BY THE SELECTIVE CONVERSION OF NORMAL PARAFFINS FROM SAID ZONE,CONTINUING SAID CONTACTING UNTIL THE VAPOR WITHDRAWN HAS AN UNDERSIRABLYHIGH NORMAL PARAFFIN CONTENT, AND THEREAFTER REGENERATING SAID METALLICALUMINO-SILICATE BY CONTACT WITH AN OXYGEN-CONTAINING GAS AT ELEVATEDTEMPERATURE.